26.4.5.6 The format_time() Function

Given a Performance Schema latency or wait time in
picoseconds, converts it to human-readable format and returns
a string consisting of a value and a units indicator.
Depending on the size of the value, the units part is
ns (nanoseconds), us
(microseconds), ms (milliseconds),
s (seconds), m
(minutes), h (hours), d
(days), or w (weeks).